over fueling problem

[tuned_nismo]

hi everyone i have a 1995 r33 gtst, only things done are an apexi filter, full 3'' turbo back (no cat), and a fmic, hks blow-off..... so car idles fine and cruises ok but once you start pushing on the gas pedal my afr's (its a narrow band) just start droppping, to as low as 10 to 1 and as soon as i hit 5 psi i hit fuel cut. So my buddy has nistune and we plugged his laptop into my car and watch what its doing and everything looks normal expect for my maf and injector which under any kind of load max out, so we thought the maf was defective and i sourced a compatible maf and install it.... no different, try removing the blow-off and installed the factory one..... no difference, checked all the piping for leaks.... all is tight and no leaks at present time.... has anyone one had this problem or something similar? the motor is a r33 series 2 motor.

[mcfly]

did you check for leaks using a pressure cap and compressed air?

Also, is your ecu stock?
Is the blow off valve staying shut?

If the maf is maxing out the injectors are going to so that is good. Is the Maf clean? Being a hot wire it is very important that it is clean.
There is no misfire when going full throttle?

What are you using to determine your afr?

[tuned_nismo]

did you check for leaks using a pressure cap and compressed air?

Also, is your ecu stock?
Is the blow off valve staying shut?

If the maf is maxing out the injectors are going to so that is good. Is the Maf clean? Being a hot wire it is very important that it is clean.
There is no misfire when going full throttle?

What are you using to determine your afr?

no i havent done a leak test using a pressure cap and compressed air, i'll look into that........

yes the ecu is stock.....
it sounds like the blowoff is opening and i even try the stock one again and same thing.......

i cleaned my maf and it was the same so i bought a compatibly maf and installed it still the same.....

when i'm full throttle the car only go to close to 4k and as soon as i hit 5 psi i hit fuel cut.....

i know its a crude setup but its my apexi turbo timer thats hook up to my o2 sensor at my ecu.... i know i need a wideband but at least its something for now

[tuned_nismo]

i had my car hooked up to my buddies nistune looked at what was going on..... he send we a screen shot......
http://i186.photobucket.com/albums/x89/onyx_gtr/robhb.png

[mcfly]

no i havent done a leak test using a pressure cap and compressed air, i'll look into that........


i know its a crude setup but its my apexi turbo timer thats hook up to my o2 sensor at my ecu.... i know i need a wideband but at least its something for now

You need to pressure test the system for leaks to ensure there are none.

Using the factory narrow band sensor is useless, more then likely what is happening is your timing is out or you have some misfiring happening. You cannot just hook up a narrow band to a turbo timer and get afr.

This is the voltage vs afr curve for a narrow band. notice the small window between rich and lean. it is only good for stoich.
http://www.vortexbuicks-etc.com/nbsensor.jpg

[tuned_nismo]

so a small update, i dont have alot of time to work on the car, havent try a boost leak tester yet, but i looking at the afm wiring so i disconnected the wiring at the afm and at the ecu, and checked resistance on the wires. pin 2 on the afm (5v reference i'm guessing) has .6 ohms on it and pin 3 (guessing reference) has 1.3 ohms on it. so im going to try cutting out the wires and running new ones